Prior to setting forth the background of the invention, it may be helpful to set forth definitions of certain terms that will be used hereinafter.
The term “Wi-Fi” as used herein is defined as any wireless local area network (WLAN) products that are based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards.
The term “Access Point” or “AP” as used herein is defined as a device that allows wireless devices (also known as User Equipment or “UE”) to connect to a wired network using Wi-Fi, or related standards. The AP usually connects to a router (via a wired network) as a standalone device, but it can also be an integral component of the router itself.
The term “client” as used herein is defined as any device that has wireless communication capabilities, specifically, the IEEE 802.11 standards. A client may be for example a smart telephone, a laptop, a tablet or a personal computer (PC).
The notation “STA” as used herein is defined in as an IEEE 802.11 client.
The term “node” as used herein is defined as general name for both IEEE 802.11 AP and IEEE 802.11 STA.
The term “serving AP” as used herein is defined in relation to one AP and one STA, wherein the STA is registered to said AP, and said AP and STA are sending and receiving data to and from each other.
The term “neighboring APs”, nodes or devices may include two (or more) co-frequency APs, nodes or devices that are within each other's sensitivity range, e.g. at least one of them can receive signals from the other in such as signal-to-noise ratio that allows decoding of signals.
The term “clear channel assessment range” or “CCA range” as used herein is a range between two IEEE 802.11 nodes, wherein at least one node can receive the other's transmission at a power level equal or larger than −82 dBm.
The term “CSMA/CA” stands for Carrier-Sense-Multiple-Access/Collision-Avoidance, representing a requirement to listen before transmitting in a multi-node wireless system that shares a common channel on the basis of first-come-first-served.
The term “preamble” as used herein describes a certain 802.11 transmitted signal modulation appearing at the beginning of each packet, that when received by other 802.11 nodes, will force them to yield channel access.
The notation “SINR” stands for Signal-to-Noise and Interference.
The term “ACK” as used herein, stands for acknowledgement or an acknowledgement signal, as for example defined as the signal transmitted from an IEEE 802.11 receiving node to the IEEE 802.11 node that has transmitted a packet to it, provided the packet was successfully received.
The term “time division duplex” (TDD) as used herein is referred to in general for systems using the same frequency spectrum for methods of communications in a time division manner such as Wi-Fi systems.
Implicit feedback is a process used for TDD protocols such as Wi-Fi, where both down and up links share the same spectrum. In the aforementioned process, the uplink channel estimated by the AP, is assumed to be identical to the downlink one—based on reciprocity principle—and is therefore is considered by the AP to represent the channel towards the client/STA
Explicit feedback is a procedure where AP transmissions are channel estimated by the STA, and then fed back to the AP, providing it with the magnitude of phase and amplitude differences between the signals as transmitted by the AP vis-à-vis as received by the client/STA, allowing it to gauge possible distortions and correct them.
The term “Legacy Long Training Field” (L-LTF) denotes a field within the IEEE 802.11 Preamble name.
The term “Very-High-Throughput Long Training Field” (VHT-LTF) denotes a field within the IEEE 802.11 Preamble name Very-High-Throughput Long Training Field.
Associated STA is defined herein as a STA that is served by a certain AP with a certain Service Set Identifier (SSID).
Non-associated STA is defined herein as a STA within the range of and non-serving AP and/or its non-serving STAs.
The acronym “NAV” stands for Network-Allocation-Vector and represents virtual carrier sense mechanism, used by a Wi-Fi transmitting message to broadcast the predicted duration of its transmission, signaling to other nodes how long will the channel be occupied
The acronym “RTS” stands for Request-To-Send, and represents a message transmitted by one Wi-Fi node to another, probing it for information about its availability to receive data, per the Wi-Fi Alliance protocol.
The acronym “CTS” stands for Clear-To-Send, and represents a positive response from the said other node to the node originating the RTS, indicating to the requesting node that the channel is clear from its point of view as well.
The notation “DURATION” is a message embedded in both RTS and CTS, representing a prediction of the future traffic about to be transmitted between two nodes that have captured the channel; other nodes that receive it, must clear the channel as long as the DURATION has nor expired; other nodes that have received the RTS but received the CTS (hidden nodes) will avoid accessing the channel, allowing the receiving node to successfully complete the reception.
The acronym “FLA” stands for Fast Link Adaptation, and represents processed that reduce transmitting side learning time of the receiver's SINR.
The acronym “MCS” stands for Modulation Coding Scheme, mapping SINR to modulation order and code rate.
The acronym “MRQ” stands for MCS request (Modulation Code Scheme Request).
The acronym “MSI” stands for MRQ Sequence Identifier, which carries MCS feedback from receiver to transmitter.
The term “null” as used herein, is a spatial pattern, created by two or more antennas, formed in such a way that minimizes the power level received by a given receiver. A “Rx Null” is a null formed by a receiver's antennas weight in order to decrease undesired signal level. A “Tx Null” is formed by a transmitter's antennas weights in order to decrease its undesired transmitted signal at remote receiver's input.
The term “nulling AP” as used herein, is a station (client) that is equipped with nulling capabilities.
The term “nulled AP” as used herein is an Access Point within CCA from a Nulling STA.
The term “neighbors list” as used herein is a list of neighboring APs and STAs within CCA range which keeps history to be checked.
The term “close neighbors” as used herein are subgroups in the Neighbors' list that are within each other's CCA range.
According to the IEEE 802.11 air protocol, two neighboring APs can download traffic over the same frequency channel to their respective STAs, as long as these APs are not within CCA range of each other.
When an RTS/CTS procedure is used, an additional condition is introduced. Namely, a legacy AP serving a respective station, must not be within CCA range of the other neighboring AP if the AP is occupying the channel.